... system Fig. E19 : IT islands within a TN-S system IMD IT system LV/ LV MV /LV TN-S system TN-S system LV/ LV MV /LV TN-S Operating room LV/ LV IT IT Hospital IMD IMD Conclusion The optimisation of the ... Earth R3R2R1 C3C2C1 MV /LV Zct MV /LV MV /LV Zs 1 Earthing schemes EIG_chap_E-2010.indb 5 04/12/2009 11:52:08 Schneider Electric - Electrical installation guide 2010 E - Distribution in low-voltage ... and actuators IT (20) TN-S, TT MV /LV LV 1 Earthing schemes EIG_chap_E-2010.indb 9 04/12/2009 11:52:11 Schneider Electric - Electrical installation guide 2010 E - Distribution in low-voltage installations...